High contrast photographic developers



Patented june 3, 1952 HIGH CONTRAST PHOTOGRAPHIC DEVELOPERS MortonSchwarcz, Highland Park, 111., assignor to The Edwal Laboratories, Inc.,Ringwood, 111.,

a corporation of Illinois No Drawing. Application April 25, 1951,

12 Claims.

This invention relates to photographic developers. More particularly,this invention relates to high contrast photographic developers. Stillmore particularly, this invention relates to high contrast photographicdevelopers having a markedly longer working life than hitherto knowndevelopers of this type.

As is well known to those skilled in the art, photographic developingsolutions usually contain at least one component selected from each offour different types of materials, namely, developing agents,preservatives, alkalies and restrainers. Most developing agents in pureform are slightly acid or neutral in reaction and exhibit feeblereducing action or even no reducing action with respect to the silverhalide latent image. For this reason, an alkali is usually incorporatedin the developing solution to accelerate the reducing action. Developingagents in alkaline solution react with and are more or less rapidlydestroyed by atmospheric oxygen. To retard or prevent this oxidation ofthe developing agent by atmospheric oxygen a preservative, such as analkali metal sulfite, is added to stabilize the developer solution. Arestrainer, such as an alkali metal bromide or benzotriazole, is usuallyincorporated in developer solutions to reduce or eliminate reduction ofthe unexposed portions of the negative or print being developed.

. In most instances it is desired to develop a negative to a state ofintermediate contrast and many photographic developing formulations areavailable that accomplish this end in an eminently satisfactory fashion.However, in certain specific fields, high contrast negatives areessential. For example, in the graphic arts, high contrast negatives areessential for the preparation of satisfactory off-set plates and similarreproduction media.

I-Iydroquinone is characterized by its inherent ability to produce highcontrast negatives. However, due to the low reduction potential of thisdeveloping agent, a very strong alkali, for example, an alkali metalhydroxide, is necessary to obtain reasonable developing speed whenhydroquinone is the sole developing agent present. Under conditions ofhigh alkalinity, the activity of this developing agent .is at such ahigh level that the density of exposed portions of the film is built upvery rapidly and a strong contrast negative results.

Unfortunately, hydroquinone in strongly alkaline solution is extremelysusceptible to air oxidation so that even in the presence ofpreservatives Serial No. 222,940

such solutions have a working life of onlya few minutes. In addition,such strongly alkaline solutions have a deleterious action on the handsof technicians using such solutions in the processing of negatives.

In orderto overcome these disadvantages of. highly alkaline highcontrast developing solu-' tions it has been the practice in the priorart to prepare high contrast developing solutions at a lower pH valuethan required for the activity necessary to produce high contrastnegatives, at.

the same time incorporating in such solutionsa material that results inthe continuous .production of a strong alkali over a considerable periodof time. Among such auxiliary agents employed in formulations of theprior art may be men-' aldehyde in turn reacts with the alkali metal;

sulfite present (as a preservative) with the production of alkali metalhydroxide in accordance,

with the reaction:

CH20+Na2SO3+H20=CH2(OI-I SOsNa+NaOH The sodium hydroxide formed as aboveindicated activates the developer to such a degree that high contrastnegatives are produced. It is to be understood that this explanationrepresents theory only and I do not wish to be bound by the explanationoffered.

High contrast developing solutions of the prior' art containingformaldehyde releasing compounds of the above nature represent aconsiderable advance over hydroquinone-sodium hydroxide solutions buteven these improved formulations are far from perfect. For example, theprior art high contrast developing solutions containing formaldehydereleasing compounds have a working life of four hours or less. In thelithographic shop this means that freshdeveloper solution must beprepared twice each shift.

I have discovered that if the formaldehyde. releasing compound found inprior art formula-f tions is replaced with a methylol derivative, for

example, a hydantoin carrying at least i one methylol group, a highcontrast developer results.

whichhas a working life of 24 hours or more; One object of my inventionis to provide an improved high contrast photographic developer solution.I I

Another object of my invention is to provide' high contrast photographicdeveloper solutions having a markedly longer working life than hithertoknown developers of this type.

Additional objects of my invention will become apparent as thedescription thereof proceeds.

For the better understanding of my invention, it will be described inconnection with illustrative but non-limiting examples thereof. Inaccordance with conventional practice, in the formulas of the examplesthe several components are listed in the order in which they are addedto the water.

Example 1 Water quarts 3 Sodium sulfite g- 120 Hydroquinone g 90 Borlcacid g Sodium bromide g 5.6 Sodium bisulfite g 10.5 Monomethylol5,5-dimethyl hydantoin g 30 Water to .gallon 1 It will be noted that theabove formulation contains hydroquinone which, because of its lowreduction potential, requires the presence of a strong alkali foractivation to. the degree necessary for the production of high contrastnegatives. However, this formulation contains no strong alkali.Nevertheless, this formulation (after. dilution with additional water ifdesired) produces, by virtue of the methylol derivative containedtherein, an excellent high contrast developing solution having a workinglife of 24 hours. or longer in distinct contrast to formulations of theprior art for the same purpose which have a working life of four hoursor less.

It is believed that the formaldehyde releasing compounds of prior arthigh contrast developer formulations decompose with the release offormaldehyde at too rapid a rate. As a result, the developing agent isconverted to the active 'form more rapidly than is required by thedeveloping process itself and as a result a large part of the highlyactive developing agent reacts.

with and is destroyed by atmospheric oxygen resulting in a short workinglife. On the other hand, the improved formaldehyde releasing compoundsof my invention are more stable and decompose at sucha rate thatactivated developing agent becomes available at approximately the ratenecessary to give the desired developing action. As a result, most ifnot all of the developing agent of the formulations of my-invention isemployed in the reduction of the latent image while little if any isdestroyed byreaction with atmospheric oxygen. Again it is to'beunderstood that this explanation represents theory only and I am in noway to be bound thereby.

If desired, a stock solution may be prepared in accordance with theabove formula with the exception that the methylol derivative isomitted. Such a stock solution is very stable. Then, just before use,the methylol derivativemay be added to give a high contrast developingsolution. By operating in this manner, a stable stock solution may beprepared by a manufacturer of photographic chemicals under carefullycontrolled conditions with respect to purity and volume of water, thecomposition, purity and weight of chemicals employed, et cetera. When ahigh contrast developing solution is-needed in the lithographic shop itis only necessary to add the required amount of the methylol derivativeto this stock solution.

Example 2 Water cc 750 Sodium sulfite g 100 Sodium metasilicate g 24Hydroquinone g Boric acid g 12 Sodium bromide g 9 Benzotriazole g 3Sodium hydroxide g 21 Monomethylol 5,5-dimethyl hydantoin g 10 Water toquart" 1 In the formula of this example, a considerable portion of thedeveloping agent is converted to the sodium salt by the sodium hydroxidepresent. Because of this it is possible to achieve a much higherconcentration of developing agent than was possible in the formulationof Example 1. This permits the preparation of a very concentrated stocksolution which may be considerably diluted to produce the workingsolution actually used. Again, the formulation of this example resultsin the production of high contrast negatives but at the same time theworking life of the developer is 24 hours or more.

Many compounds, other than the monomethylol 5,5-dimethyl hydantoinspecifically mentioned in the above examples may be employed toaccomplish the objects of my invention. Among these may be mentionedmonomethylol l-alkyl hydantoins, monomethylol 3-alkyl hydantoins,monomethylol and dimethylol 5-alkyl hydantoins, monomethylol 1,5-dialkylhydantoins, dimethylol 5,5-dialkyl hydantoins, monomethylol anddimethylol hydantoins, monomethylol and dimethylol ethyleneurea(monomethylol and dimethylol 2-imidazolidone), monomethylol anddimethylol urea and the like.

While my invention has been described in connection with the use ofhydroquinone as the developing agent, other developing agents,especially those of low reduction potential, may be used.

Be it remembered, that while my invention has been described by'means ofnumerous examples thereof, these are illustrative and non-limiting andit is to be understood that my invention covers all changes andmodifications of the examples thereof, herein chosen for purposes ordisclosure, that do not constitute departures from the spirit and scopeof my invention.

I claim: I

1. An aqueous photographic developing solution comprising a silverhalide developing agent, an alkali metal sulfite and a methylolhydantion.

2. An aqueous photographic developing solution comprising hydroquinone,an alkali metal sulfite and a methylol hydantoin.

3. An aqueous photographic developing solutioncomprising a silver halidedeveloping agent, an alkali metal sulfite and a material selected fromthe group consisting of a monomethylol hydantoin, dimethylol hydantoin,a monomethylol l-alkyl hydantoin, a monomethylol S-alkyl hydantoin, amonomethylol 5-alkyl hydantoin, a dimethylol 5-alkyl hydantoin, amonomethylol 1,5-dialkyl hydantoin, a monomethylol 3,5-dialkylhydantoin, a monomethylol 5,5-dialkyl hy-' dantoin, a dimethylol5,5-dialkyl hydantoin, a monomethylol 1,5,5-trialkyl hydantoin and amonomethylol 3,5,5-trialkyl hydantoin.

4. The composition of claim 3, further characterized by the fact thatsaid developing agent is hydroquinone.

5. An aqueous photographic developing solution comprising a silverhalide developing agent, an alkali metal sulflte and monomethylol 5,5-dimethyl hydantoin.

6. An aqueous photographic developing solution comprising hydroquinone,an alkali metal sulfite and 3-methylol 5,5-dimethyl hydantoin.

'7. In preparing photographic images, developing a latent silver halideimage by an aqueous solution containing a silver halide developingagent, an alkali metal sulfite and a methylol hydantoin.

8. In preparing photographic images, developing a latent silver halideimage by an aqueous solution containing hydroquinone, an alkali metalsulfite and a methylol hydantoin.

9. In preparing photographic images, developing a latent silver halideimage by an aqueous solution containing a silver halide developingagent, an alkali metal sulfite and a material selected from the groupconsisting of a monomethylol hydantoin, dimethylol hydantoin, amonomethylol l-alkyl hydantoin, a monomethylol 3-alkyl hydantoin, amonomethylol B-alkyl hydantoin, a dimethylol 5-alky1 hydantoin, amonomethylol 1,5-dialkyl hydantoin, a monomethylol 3,5-dialkylhydantoin, a monomethylol 5,5-dialkyl hydantoin, a dimethylol5,5-dialkyl hydantoin, a monomethylol 1,5,5-trialkyl hydantoin and amonomethylol 3,5,5-trialkyl hydantoin.

10. The process of claim 9, further characterized by the fact that saidsilver halide developing agent is hydroquinone.

11. In preparing photographic images, developing a latent silver halideimage by an aqueous solution containing a silver halide developingagent, an alkali metal sulfite and monomethylol 5,5-dimethyl hydantoin.

12. In preparing photographic images, developing a latent silver halideimage by an aqueous solution containing hydroquinone, an alkali metalsulfite and monomethylol 5,5-dimethyl hydantoin.

MORTON SCHWARCZ.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS

1. AN AQUEOUS PHOTOGRAPHIC DEVELOPING SOLUTION COMPRISING A SILVERHALIDE DEVELOPING AGENT, AN ALKAKI METAL SULFITE AND A METHYLOLHYDANTION.